Figure 3.

Correlation of neutralizing activity of infection-derived antibodies with binding and avidity. A, B, Correlation of neutralization titers, expressed as inhibitory dilution 50% (ID₅₀), with wild-type (WT) spike-specific immunoglobulin (Ig) G measured with the in-house enzyme-linked immunosorbent assay (ELISA) (A) or with the SeroKlir commercial ELISA from Kantaro Biosciences (B). Abbreviations: AU, arbitrary units; AUC, area under the curve. C, D, WT spike IgG avidity index (AI) (C) and avidity measured using biolayer interferometry (D). Abbreviation, K_dis, constant of dissociation. In C, samples with an AI <35, indicated by the dotted line, are considered to have low avidity. WT refers to the sequence of the original Wuhan-Hu-1 severe acute respiratory syndrome coronavirus 2 isolate. Each symbol represents a single participant. Pearson correlation was used; significance and correlation coefficients are shown. A, B, D, n = 34; C, n = 20.